Wavelength-agile single-frequency laser diodes are being regarded as essential components for various telecommunication applications. Such laser diodes can be used as backups for fixed-wavelength transmitters. With wavelength division multiplexing (WDM) communication systems operating on a large number of optical wavelength channels, a large number of fixed-wavelength transmitters have to be kept as spares, which produces high additional costs. However, with a widely tunable laser that is able to operate on any of the available optical channels, costs can be significantly reduced. Tunable lasers are becoming enabling key components for optical networks. They can be used for functionalities like packet switching, wavelength conversion and light modulation, thereby making optical networks more flexible. Besides these applications, tunable lasers or laser diodes are also attractive light sources for sensing applications as well as for Fiber Bragg Grating (FBG) based sensor devices.
There is a need in telecommunication for tunable lasers, especially integrated widely tunable lasers. Currently industry companies use different methods to realize tunable lasers, for example such as advanced grating structures such as; DSDBR (Distributed Supermode Distributed Bragg Reflection) or SGDBR (Sample Grating Distributed Bragg Reflection) or usage of multiple DFBs (Distributed Feedback) with SOAs (Semiconductor Optical Amplifiers). Currently available tunable lasers have demanding processes or suffer from large footprint. Both lead to high cost due to waste of chip space or complexity of fabrication process and complexity of operation.
There is a need to provide a tunable laser that is easy to manufacture, in particular a tunable laser that requires small chip space and that may be easily produced in a chip fabrication process.